Phase measuring device



March 1, 1949. J c. SPINDLER PHASE MEASURING DEVICE Filed March 25, 1944 AMPLIFIER DETECTOR MAGNIITUDE BALANCER OUTPUT INVE4NTOR J'oJzp/r C. IF/(V01. 5e

BY flfl ATTORNEY Patented Mar. 1, 1949 PHASE MEASURING DEVICE Joseph C. Spindler, Brooklyn, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application March 25, 1944, Serial No. 528,147

8 Claims.

This invention relates to phase measurements and to phase measuring devices for measuring the difference in phase angle between twoalternating voltages or between one alternating voltage and a reference voltage.

An object of the invention is to provide a simple device and a method for measuring the difierence in phase angle between two alternating voltages.

Another object of the invention is to provide a device and a method formeasuring the difference in phase angle between two alternating voltages in which the angle can be read directly on a meter.

Still another object of the invention is to provide a phase measuring device utilizing a goniometer.

Other objects and objects relating to the arrangement and electrical connections of the various parts of the device will be apparent as the description of the invention proceeds.

The invention-is illustrated in the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a goniometer used to explain the invention;

Fig. 2 is a schematic circuit diagram of the phase measuring device of the invention; and

Fig. 3 is a circuit diagram of one form of magnitude balancer used in the device of the invention.

The device of the invention is based upon the principle that if two alternating voltages are applied to the two stators of a goniometer, the voltage induced in the rotor of the goniometer is a function of the magnitudes of the voltages in the stators, the phase angle and the angular position of the rotor. Bydetecting the voltage induced in the rotor of the goniometer and measuring the output for different positions of the rotor and adjusting the magnitude of the output/for a certain position of the rotor, it is possible to read the phase angle between the two voltages directly upon the output meter when the rotor of the goniometer is turned to another position.

Referring to Fig. 1, a goniometer l is indicated.

diagrammatically with stator coils Sland S2 arranged in the usual manner at right angles to each other and a rotor coil R arranged to rotate in the plane of the stator coils. Assume that one alternating voltage is applied to the stator coil SI and has a value E1, and that the second alternating voltage is applied to the stator coil S2 and has a value E2. Then the voltage induced in the rotor coil R has a valueEs. As-

sume also that the position of the rotorfor inducing a maximum voltage from the stator coil SI is called 0". We can then say:

If the |E1|=IE2L then the function describing the relative variation in IE3| is As will be shown, the factors 0 and IAEaI can be expressed in terms of a single variable E3 min E max where E3 max is themaximum output obtained as the rotor of the goniometer is turned and E3 min is the minimum output as the rotor is turned. These maximum. and minimum output voltages are obtained because the relative polarity between the rotor and stator coils changes as the rotor is turned. In one position of maximum coupling the voltages add in the rotor and in the other position they subtract.

Then

E min E3 max That is, it can be shown that under certain conditions the phase angle can be determined from the ratio of minimum rotor output to maximum rotor output as the rotor is turned through an angle large enough to determine these two values.

If we first consider the case where IE1I==|E2|=a constant, and =0, then IE3I=KE1 cos 0+KE2 cos (0) or, since E1=Ez,

|E3I=k[cos 6+cos (90-0)] where Ic=KE1.

It can then be shown that, because of the difference in relative coil polarity for different positions of the rotor, [E31 will be a maximum at a position 0 which is an odd multiple of 45 and a minimum at a position also an odd multiple of 45 but 90 removed from that giving the maximum value. Hence;

where A is the component derived from E1 and is equal to and B is the component derived from E2 and is equal to and If now we consider the etfects ot phase angle.

control knob M. The output of the amplifier and detector I4 is delivered to a direct current meter l5 which may be any current indicating device for measuring the variation in the D. C. component of the detector output, such, for example, as a D. C. microammeter, and which may be calibrated to read the phase angle directly.

The measurement may 5be-madedn the: followingamanner-rzrEirststhe rotor 4 of the goniometer I is rotated by means of the knob 1 until the pointer registers 0, at which time the rotor coil wilLbeparallel to the stator coil 2. Voltage will then be' induced in the rotor coil 4 from the stator coil,2;;and-,;not1r from the stator coil 3. The doat these and 5m9nsr fih s 155: tectedroutputtvol'tage is then inspected on the understood that o equals the differencetin phase; angle between E1 and E2, then M ie In Fig. 2 is shown a schematic circuit diagram of adevice for measuring the difference ,inphase; angle a between: two; voltages inc; accordance @with indicating metevlfi-and the output adjusted to a convenient valueby: adjusting the control knob lf" provided on the magnitude balancer l3 for adjusting the amplitude of the voltage E1. The

reading on the output meter is noted. Thereupon the; rotor; coil 4-; is rotated until the pointer is; aligned with the 1 90 position wherrthe rotor;

coll te-twill. be; parallel: to the stator coils Bland;

voltage ninducedi in 'it;. will; beifrom that coil. The..-

reading on the output-meter isagain-noted. If:

amplitude of thew voltage. E21 is adjusted until the readingpof theioutput meterzi's-thesame as before Whom this isdone the two voltages E1 andE'zwill be equal-in their:: effect on the rotor 4 oi the goniometer l.

The rotor tot-the goniometer l is then set-at either. or 1-35 whichever gives: the larger output, and the amplifier and detector 14 is adjusted" by means of the: knobit", provided for that purcalculatignsn Showv t t, for; pose;s'o tliatthe'output' of-the amplifier=maybe raised or lowered to bring the; needle of-the in dicator meter l5 to a reference 'line- [5" which may conveniently correspond} to' the indica- Then the goniometer coil F tion on the scale. U is---rotated to the or "45 position-,- whichever may beread" directly onthe :scale of the meter which is' calibrated for-thatpurpose in accord-'- the-: exp1anati0n. given above; goniometer 7; 50' ance witlr'the equation. This reading will alwayshas; two. stator :=coi-ls, 2 and: 3, corresponding; tothe; stator coils S1 :and: S2; oi Fig.1 l'uandzaqrotorscoil 4corresponding .toqthe- 'rotor- COHTRQQIQ Fig.1. The rotor is mounted upona suitableeshailt indie, cated by the dotted line 5\ uponswhichl is also mounted a pointer 5 and a knob Tfo'r manually rotating the shaft. The pointer firrotatesrinlcoe. operation withva dial 8,and maybe provided with suitable detents 9 which cooperate with a projection ID on the pointer 6, so that'the-poin-ter may be positioned accurately at a desired-angle.

The-source of one-voltagegEi, is'indicated at It and the source ofth'el other voltage, E2 is indicated at i2. These voltages are fed through a magnitude balancer l3 which is forthe purpose"of adjusting'the amplitude ,of these Voltages" as delivered to the stator coils 2* and" 3; adjusting knobs H and l2l'being:providedl1vfor that purpose. A suitable circuit for this magnitude b912,, ancer will be described llater."

The output of the rotor coil 4. 15 delivered tq. amplifier and detector M which may be anytsuit able amplifier and detector for alternating current of the frequency being used, the gain of the amplifier being adjusted by means of the give the correct phase angle, sincethemaximuin output isalways adjusted 'to coincideywith: the

reierence mark" on the meter."

h a e e e erm r n he e e m h be pl ce i' q who th me ith t e n m m utp adinainwhich ase he min mum, put; would always be adjustedto itxand 'the' maximum lt es re qual-w ndshe efo athe m w ain dif risthi c n i ions *gives the-smalleroutput"; whereupon the-phase atet e en inatio of: he. nh see neleecan; be}.

. In Fig. 3 is shown a. circuit two of which may be used in the magnitude balancer l3 for adjusting the magnitude of the input voltages without changing the phase thereof. In its simplest form the circuit comprises a pentode tube l6 provided with a variable resistor I! in its cathode circuit which is shunted by a condenser l8. The input voltage is delivered across a resistor 19 which is connected between the control grid and ground. The suppressor grid is connected to the cathode and the screen grid is given a suitable potential through a resistor 20 from a source of positive potential, indicated at 2!, the screen grid being bypassed to ground through a condenser 22. The plate of the tube I6 is provided with a suitable positive potential through a resistor 23 from the source of positive potential 2|. A coupling condenser 24 applies the voltage variations from the plate of the tube across an output resistor 25 which is connected across the stator coil.

Adjustment of the resistance I! in the cathode circuit will alter the bias of the tube so as to change the output voltage. It will be understood that the components of the circuit are properly chosen to prevent change of phase in the output circuit when the bias resistor is adjusted. One circuit is provided for the input voltage E1 and another for the input voltage E2, the adjusting knobs II and I2 being provided to make the adjustment on the bias resistors. Other circuits for making this balance adjustment may be provided if desired.

With proper selection of components for the two circuits of Fig. 3 used in the magnitude balancer I3 there should be no phase shift in the output'voltages with change in setting of the variable resistors in the cathode circuits. However, if there should be any noticeable difierence in phase between the two circuits, it is possible to determine what that phase difference is by feeding a single alternating voltage into the two stator coils simultaneously. The procedure outlined above can then be followed to determine the indicator reading, which should be 0. If it is not 0, a simple network arrangement for shifting the phase of one balancer circuit with respect to the other may be used to make the reading 0. Then the entire system should operate properly.

While the invention has been disclosed in connection with a mechanically operated goniometer, other types of goniometers, such as an electronic type, may be used.

From theabove description it will be seen that I have provided a method and a means for accurately measuring the difference in phase angle between two alternating voltages, and that by means of my invention this difference in angle may be read directly on a specially calibrated meter.

Various modifications of the invention may be apparent to those skilled in the art and I do not therefore wish to be limited to the specific method and structure disclosed except by the limitations defined in the appended claims.

What is claimed is:

1. The method of determining the difference in phase angle between two alternating voltages of the same frequency which comprises causing said voltages to produce fields of force at an angle to each other, placing a conducting element successively in a plurality of predetermined positions in said fields whereby voltages are induced in said element, measuring the voltages induced in said element in each of said positions, adjusting the 6, two voltages to have a predetermined constant ratio between them, adjusting the voltage induced in said element when in one position to a predetermined reference value, and reading the phase angle between the two input voltages directly on a meter when said element is in another position.

2. The method of determining the difference in phase angle between two alternating voltages of the same frequency which comprises impressing said voltages on the stator coils of a goniometer with a predetermined constant ratio between their amplitudes, detecting the output of the rotor coil of said goniometer, adjusting the angle of said rotor coil to receive maximum induced voltage from both said stator coils, as indicated by the detected output, measuring the detected output of said rotor coil, adjusting the angle of said rotor coil to receive minimum induced voltage from both said stator coils, as indicated by the detected output, again measuring the detected output of said rotor coil, and taking the ratio of the smaller measurement to the larger measurement as a measurement of the difference in phase angle between said two first mentioned voltages.

3. The method of determining the difierence in phase angle between two alternating voltages of the same frequency which comprises impressing said voltages on the stator coils of a goniometer with a predetermined constant ratio between their amplitudes, detecting the output of the rotor coil of said goniometer, applying the detected output to a meter, adjusting the angle of said rotor coil to receive maximum induced voltage from both said stator coils, as indicated on ,said meter, adjustin the angle of said rotor coil to receive minimum induced voltage from both said stator coils, as indicated on said meter, adjusting the magnitude of the detected output in one of said angular positions of said rotor coil so that said meter will register a predetermined reference value, and reading the phase angle between said two first mentioned voltages directly on said meter when said rotor coil is in the other of said angular positions. I

4. The method of determining the difierence in phase angle between two alternating voltages of the same frequency which comprises impressing said voltages on the stator coils of a goniometer with a predetermined constant ratio between their amplitudes, detecting the output of the rotor coil of said goniometer, applying the detected output to a meter, adjusting the angle of said rotor coil to receive maximum induced voltage from both said stator coils, as indicated on said meter, adjusting the magnitude of the detected output of said rotor coil so that said meter will register a predetermined reference value adjusting the angle of said rotor coil to receive minimum induced voltage from both said stator coils, as indicated by said meter, and reading the phase angle between said two first mentioned voltages directly from said meter.

5. A phase measuring device comprising a goniometer having two galvanically independent stator coils and a rotor coil, means to deliver a first alternating voltage of a given frequency to a first stator coil of said goniometer, means to deliver a second alternating voltage at the same frequency to the second stator coil of said goniometer, means for adjusting the relative voltage of said stator coils to obtain a constant ratio therebetween, a detector having its input connected to said rotor coil, a meter connected to said detector and adapted to measure the detector output. and means to adjust the position of said rotor coil.

aaeeaeeiezz statorrcoilsrand: azxrotor: coil, meanssto applyi'azfirst; alternating :voltage atoa; first statorvcoil; I oi? said: goniometer, means .to adjust them-amplitude; otxthegvoltagea applied: to saidzzfirstistatori coil; means;-..toiapply' a second alternating: voltageta the=second statori coilof said" goniometen. means to adjust. the amplitude :of the-voltage. applied. to said second: stator coil. to; establisha constantvoltage ratio betweensaid-stator. coils; an; ampli:-. fier and a detector'connected tos thezoutput'of'said retort: coi-1,,. means. .to. measure the; output :-.of.:said; detector, meanswto adjustrthe output ofrsaictamq plifier; and means. to positionasaidrotor: coils. in V one. Of aplurality; of rotary positions.v

8.. A:= phase: measuring) device comprisinga goniometer having: two .galvanically independent: stator- ;v coils: and? a. rotors'coil, means: to apply aflrst alternating: voltage. to a: firststaton coilioi saidgoniometer, means; to adjust the amplitude otth'ex. voltage applied to said first -stater coil; means rto: applyasecondi alternating voltageto Number Name. Datev 1,365,579 Appleby et al. Jan.-z 11,, 1921. 1,435,9L. Robinson N031;- 21, 1922 1-;z15ne19. Goldschmidtfetak June; 13;;19291 35; 2,202,885. Zuschlag' June 1940 Alford Sent: .23; 1941 8? theisecondnstators coil; ofisaddsigoniometerg; means tmadjnst'the amplitude rofzthewoltage applied to said. second; statorecoil; amamplifiert connected .to

thmoutput ofssaidmotor'wcoil; meansgtoisadiusizthee gainot-saidiamplifien-a:detectonconnectedatmthea output of; said. amplifier, means toadiust; said rotor. to. any one of apluralitm of rotanwpositionso two of which are those which produce andminimumrvoltage-from said: statoli coils-,: and:

a-metenconnected. totheoutput of; said;.detector;.

saidmeter being-calibrated in aecordancefiwith the;

equation lEtmini. i- 'o rti. l'Esl l'f I W W' where l lib- 1min L is. said; mini-mum voitage: from.

saidstaton coils; and:- |Esamaxel= isvsaidtmaximum". voltagairom saidstaton: coils; and; (pt-equals. the difleren'ce.-.in phase angle. .betweenisai'd' first and. second alternating; voltages, a-- predetermined. value for one, ofqtlie terms. in the. lefthand: side oflthe equation, being used as amreference point.

forsaid-calibrationr J OSEPHKC, SPINDLER.

REFERENCES'.CITED Theafollowing references areiofiTrecordi in." the fiiea oi; this-patent UNITED" STATESPATENTS 

